How will climate change affect restoration of the Florida Everglades?

How will changes in future climate, including rising sea level, increased temperature and evaporation, and perhaps less rainfall and longer droughts, affect the success of the ongoing multi-billion dollar Comprehensive Everglades Restoration Program?

The effects could be dire, and climate change needs to be factored into restoration planning, according to Everglades scientists and resource managers who recently gathered (Feb 2013) in Boca Raton to address this critical issue. The event was hosted by Florida Sea Grant, the U.S. Geological Survey and the Center for Environmental Studies at Florida Atlantic University.

By way of background, the Florida Everglades is a vast and diverse ecosystem stretching from the headwaters of the Kissimmee River near Orlando to Florida Bay. Under natural conditions, water flowed by gravity from the top to bottom of this ecosystem, to a large extent as a broad sheet flow.

Today the ecosystem is markedly different, having been altered by nutrient pollution and the construction of dikes, levees and canals to drain areas for agriculture and flood protection. These human alterations have resulted in a 50% loss of area and nutrient-induced changes in ecological function. Yet, the Everglades remains a national treasure – an International Biosphere Reserve, a World Heritage Site and a Wetland of International Importance.

Work is now underway on one of the world’s largest restoration programs to restore some of the Everglades’ historic hydrologic and ecological functions. This program, authorized by Congress in the 1990s, did not explicitly consider effects of climate change on the project’s outcome. Today, however, we realize that sea-level rise may have severe impacts at the southern end of the ecosystem, and changes in rainfall, temperature and evaporation may have even broader reaching effects.

The workshop involved a formal evaluation of possible consequences of these climate changes on success of the restoration project. Attendees identified research gaps where scientists were not able to make accurate predictions of impact.

Just as in the planning process that resulted in the authorized restoration project, modelers at the South Florida Water Management District ran a regional model of water flows and storage in the system, but this time introduced a 2060 climate scenario of increased sea-level rise, increased temperature, increased evaporation, and plus or minus 10% of current rainfall.

Experts in the ecology of different parts of the regional system, including Lake Okeechobee , the Everglades Ridge and Slough Habitat, and the southern mangrove marshes looked at the model output – water levels over a simulated 30-year time period, comparing the climate-change scenario with a ‘base’ scenario driven by current climate. They discussed how climate change is expected to affect those ecosystems.

The results were striking. While a future with both higher temperatures and more rain may not spell a large change in the region, a situation of both warming and less rain could result in extreme low water levels in Lake Okeechobee that would be too low to support viable fish populations or meet water supply demands.

It could also result in extreme drying and probable large-scale fires and peat loss in the northern Everglades, and large-scale saltwater intrusion into the south end of the system, possibly to a degree that wetlands are changed to open sea water.

Of course these are only scenarios, and no one knows right now what the climate will be like in 2060, but these scenarios bracket what might happen, as they are based on results of three different regional climate models.

The exercise was useful in identifying areas of uncertainty, where scientists could not make reasonable projections about what changes might happen. As noted, these are areas of high priority for research.

The exercise also engaged resource managers in a discussion about climate change, and may lead to it being more seriously considered in this huge and costly restoration program that to date ignores that factor.

The program leaders anticipate publishing the results of this meeting as a special series of papers in the international journal Environmental Management, because the case study is highly relevant to large-scale restoration projects elsewhere in the world.

Dr. Karl Havens has 25 years of professional experience in aquatic research, education and outreach, and has worked with Florida aquatic ecosystems and the use of objective science in their management for the past 15 years. His area of research specialty is plankton ecology and the eutrophication of lakes and estuaries. He is particularly interested in how natural and human-related stressors impact the structure and function of plankton and other components of shallow aquatic ecosystems.